1. Field of the Invention
The present invention relates to devices and methods for measuring one or more alignment characteristics of a rear suspension of a vehicle, such as tracking (thrust angle), offset, toe-in and toe-out, and length characteristics.
2. Background of the Invention
Tracking problems can arise in vehicles as a result of Diamond damage or misalignment of the rear wheels. methods of checking tracking include, for example, attaching surveyor's string to a frame, suspension, or other component behind a rear tire; pulling the string across the tire, such that the string is just touching the outer front surface of the tire (i.e., such that the string is substantially parallel with the outer surface of the tire); extending the string to a point further forward on the vehicle, such as the cowl area, and measuring the distance between the string and the frame at that point. This procedure is then repeated on the opposite side of the vehicle. If the two measurements are not equal then adjustments may be required. Also, for each side of the vehicle, while the string is pulled across and parallel to the outer surface of the tire, the tire can be rotated to check for run-out, i.e., variation in the tire or a bent wheel. A similar but more sophisticated method uses a laser plane on the tire rather than surveyor's string to establish a straight line parallel to the outer surface of the tire.
Methods for measuring offset include measuring the distance between the center of the wheel and a point further forward on the frame, such as the frame's centerline. This procedure is then repeated on the opposite side of the vehicle. If the two measurements are not equal then adjustments may be required
Other methods for determining these and other alignment characteristics suffer from a number of problems and disadvantages, including, for example, that they can be cumbersome, inconvenient, or time-consuming to employ and that they can result in significant inaccuracy.